Ruin elementals were massive earth elementals approximately 14 feet (4.3 meters) tall and 7,000 pounds (3,200 kilograms) in weight. They were composed of rubble from the ruins they guarded. Over time, this rubble slowly eroded into smaller pieces, so that the oldest ruin elementals appeared to be composed of gravel.
Ruin elementals cared for nothing except protecting the fallen cities and fortresses they were set to guard. When those areas were not threatened, they were relatively benign.
Ruin elementals existed to protect ruins wherever they might be. Thus, these creatures could be found in tundras, deserts, and other hospitable and inhospitable places. Due to their remote dwelling places, they were little more than legends to most of Faerûn.